Factors affecting the efficiency of Rhizobium rhizogenes root transformation of the root parasitic plant Triphysaria versicolor and its host Arabidopsis thaliana

Pradeepa C. G. Bandaranayake,John I. Yoder

doi:10.1186/s13007-018-0327-2

Abstract

BackgroundRhizobium rhizogenes transformation is commonly used to generate transgenic roots traditionally called hairy roots, for both investigative and commercial applications. While fertile plants can be regenerated from transgenic roots, the transgenic roots are more typically used directly, either to investigate root biology or to produce valuable secondary metabolites. Hairy roots have been particularly useful for genetic studies of rhizosphere interactions; including the recognition of host plant roots by the roots of parasitic angiosperms.ResultsIn this manuscript we analyzed various environmental, nutritional and procedural conditions for their effects on transformation of the model hemi-parasitic plant Triphysaria versicolor and Arabidopsis thaliana, one of its hosts. We first examined the effects of media, gelling agents and co-incubation times on Triphysaria root transformation and determined that while all three affected transformation rates, the media were the most significant. Once those primary conditions were fixed, we examined the roles of seedling age, explant type, acetosyringone, temperature and illumination on Triphysaria hairy root transformation rates. Using the optimized procedure approximately 70% of Triphysaria seedlings developed transgenic roots as judged by expression of YFP. These conditions were then used to transform Arabidopsis and similar transformation rates were obtained.ConclusionsAnalyses of root transformation factors provides a method recovering transgenic roots from both parasitic plants and their hosts at high frequency. In addition to providing an effective in vitro approach for genetic investigations of parasitic plant-host plant interactions, these results are applicable to genetic studies of non-parasitic plants as well.

Highlights

Rhizobium rhizogenes transformation is commonly used to generate transgenic roots traditionally called hairy roots, for both investigative and commercial applications
We previously demonstrated that R. rhizogenes transformed Triphysaria roots form haustoria upon treatment with haustorial inducing factors and that these haustoria are functional and able to transport regulatory, hairpin generated RNAi molecules from host to parasite [25,26,27]
This paper describes the optimization of R. rhizogenes transformation of the root parasitic plant Triphysaria and its host Arabidopsis

Summary

Introduction

Rhizobium rhizogenes transformation is commonly used to generate transgenic roots traditionally called hairy roots, for both investigative and commercial applications. While fertile plants can be regenerated from transgenic roots, the transgenic roots are more typically used directly, either to investigate root biology or to produce valuable secondary metabolites. Rhizobium rhizogenes transformed roots can be regenerated into mature fertile transgenic plants [4], but more commonly transgenic root cultures are used directly to produce desirable compounds or to study gene function. Root cultures provide a useful means for producing desirable molecules that are naturally made by plants and secondary metabolites have been isolated from hairy roots of over 150 plant species [7]. R. rhizogenes is used to transform foreign genes into roots in order to produce novel products not present in the targeted host plant, such as Nicotiana benthamiana roots that produce a tumor-targeting therapeutic antibody with a glycosylation profile similar to that of humans [10]

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Conclusion